Kenyan authorities say they are still holding eight people in connection with the deadly four-day siege at a Nairobi shopping mall.

Interior Minister Joseph Ole Lenku told reporters Friday that authorities have released three other suspects.

Earlier this week, officials said five suspected militants were killed as troops and police worked to regain control of the Westgate mall.

The official total death toll from the siege stands at 72.

Investigators continue to sift through the wreckage at the partially collapsed mall. On Friday, the Kenyan Red Cross said 59 people remain missing following the attack.

Lenku said no additional bodies have been recovered from the site.

"According to police records, there are no formal or official reports of missing persons who could have been at the mall at the time of the attack."

The Somalia-based al-Shabab extremist group claimed responsibility for the attack and is vowing to carry out other acts of violence against Kenya.

On Twitter Friday, the militant group said its attack on the Westgate mall was "just the premiere of Act 1."

Al-Shabab says it wants Kenyan forces to withdraw from Somalia. Kenyan forces entered neighboring Somalia two years ago to help fight the militant group, which has been fighting to turn Somalia into a strict Islamic state.

The Associated Press said Friday that investigators had recovered a vehicle that was believed to have been used by some of the attackers.

Human Rights Watch urged Kenyan authorities to "swiftly" catch and prosecute the mall attackers. In a statement, the group's Africa director, Daniel Bekele, said "nothing justifies the cruel contempt for human life" that the attackers had shown.

In another development, the International Criminal Court announced it has extended Kenyan Deputy President William Ruto's absence from his trial until Wednesday.

The ICC said it granted the extension to allow Ruto to attend a memorial service for mall victims on Tuesday.

Ruto faces charges of crimes against humanity for his alleged role in the deadly ethnic violence that followed Kenya's 2007 election.